Treatment of sheets, thin bars, and the like



UNITED STATES PATENT OFFICE TREATMENT OF SHEETS, THIN BARS, AND THE LIKERussell R. Smith, Hillard E. Miller, and Ralph H. G clder, Ashland, Ky.,assignors to The No Drawing. Application March 10, 1937,

Serial No. 130,216

1 Claim. (Cl. 148-8) Our invention relates to a treatment for that thesheet is later enameled, plated, bondersheets, thin bars'and thelike,'by which we preized or otherwise treated. pare them for suchsubsequent treatment as en- Since the pickling bath usually containssulameling, painting, ducoing, bonderizing, nickelphuric acid, eitheralone or in combination with 5 plating, galvanizing, cadmium plating andalloy other acids such as muriatic acid, the reaction 5 plating. Sheetswhich are ultimately to be used of the acid on iron or steel will formsulphates or for any of the above named purposes must be of chlorideswhich are not removable with lime. very high quality, in order that thevarious coat- We have found that the various above menings will adherewell to the base metal. It is tioned deleterious results may beeliminated by a .o then necessary to reduce the metal to the propercyanide neutralizing bath. For this purpose, thickness and to have thefinal sheet perfectly we prefer to use sodium cyanide, although poclean,so that it will bond with the coating which tassium cyanide or othercyanide solutions will is t be app]ied accomplish the same purpose. Theafore-men- Briefly, we prefer to carry out our process on tionedsulphates are readily soluble in a solu- 13 sheets, strips, thin bar andthe like in the foltion of sodium cyanide and they are therefore 15lowing manner: Commencing with a slab, we hot removed from the surfaceof the sheet and th roll this slab, for example, on a continuous hotsheet is left chemically clean. strip mill or a hot sheet jobbing mill,to thin bar The neutralizing bath, which contains a suitgauge. We thenpickle the material and then able cyanide such as sodium cyanide, isprefreduce it to final sheet gauge either on a cold or erably held at atemperature of from 140 to a hot mill. If the preliminary steps of thisproc- 180 F. although higher or lower temperatures ess as above outlinedhave been carried on so may be used, and is maintained at a strength ofthat we now have a long strip of metal, we may om 1 t0 u ce f od myanide per proceed directly to normalize, while if we have on ofSolution- The p ture of the bath short lengths of metal, we prefer tostitch them will depend upon the type of drying to which 25 so as toproduce 'a long strip. We then northe product is to be subjected, andalso upon the malize the strip and pickle it. We then prefconcentrationof the solution. We have found erably pass the strip through a hydraulicspray of that very much weaker concentrations may be cold wtaer at highpressure (for example 300 used and also that concentrations up to one or3 lbs. per square inch) and then through a low more c s per al could beused- Experi- :0 pressure cold water spray (for example 80 lbs. ence hasshown, however, that increased amounts per square inch) in order to washit. We then of sodium cyanide do not materally improve the pass thesheets or strip through a tank containproduct. The sheets are immersedin the cyanide ing a cyanide solution and then again wash the tank fromfour to five seconds, up to thirty-five trip d dry it by passing itthrough parallel or forty seconds, depending on the speed with 35 highpressure jets delivering either hot air, steam, Which the strip passesthrough the tank. The or high pressure hot water, and then through aSpeed With wh h t e St p passes through the drying furnace which ismaintained at a temtank is a function of the preceding pe s,

I perature sufficient to complete the drying of the namely normalizingand pickling.

sheet. The sheets may then pass through several An after treatment ofcyanide neutralized 40 loop pits and are then sheared to length. sheetsmay comprise, for example, a temper roll It will be noted that in theabove series of through one or more passes of temper mills, steps, wepass the sheets or strip through a tank which may be of the two, threeor four-high containing a cyanide solution. The purpose of variety.These passes may be made with water,

this cyanide solution is to neutralize the sheets with steam, with gas,or dry. The sheets may after the pickling step. It has been usual tothen be roller levelled. Another after treatment use a lime bath forpickling purposes, but we have which we have found to be desirableinvolves the found that a lime bath is not always satisfactory, aftertreatment discussed above, followed by box because it merely neutralizesthe portions of free annealing at temperatures from 809 to 1450" F.

5 acid which remain on the sheets and does not sheet temperature.Various gases may be introremove the usual pickling. deposit or smudge.duced into the annealing box to prevent oxi Furthermore, since lime isbut slightly soluble in dation of the sheet surface. water, it adheresto the sheet as free lime which Another after treatment which we havefound. later causes trouble because it promotes rust desirable mayinclude the treatments above outand has other detrimental effects, inthe event lined, followed by a further temper rolling on 55 two-,three-, or four-high mills, either wet or dry or both, and a rollerleveling.

We have found that the box annealing step changes any traces of sodiumcyanide which may remain on the sheet into sodium carbonate.

Where the sheets are to be subsequently galvanized, they are prepared asoutlined above. Various routings may be used preceding the cyanidetreatment, depending on the temper required in the galvanized product.After the cyanide treatment, the sheets are dried by one or more of theaforesaid mentioned drying media and roller leveled in preparation forthe galvanizing operation. We have found that cyanide treated sheets arefree from injurious sulphates and as a result the characteristics of thegalvanized product are very much improved. We have noted an improvedadherence of the galvanized coating and have been able to obtain abetter control of the coating and an improved appearance. Thegalvanizing operation may, of course, be done with sheets or coils.

We may use our sodium cyanide neutralizing in the preparation of thinbar for cold reduction either in sheets or coils. For this purpose thesodium cyanide is used as a neutralized after pickling, as aboveoutlined, and the sheets rolled from thin bar so treated, will have abetter appearance due to the fact that a clean white thin bar is used.In this product we have noted im proved bonderizing characteristics,improved en amel bonding, improved plating characteristics and greaterresistance to rust. The thin bar referred to above, may vary from .050to .250 in thickness and may be up to 96 inches wide.

The above mentioned cold reduced sheet may be used with the heattreatment or it may be normalized and box annealed at varioustemperatures up to 1450" F. or it may be box annealed alone. Inaddition, various tempering processes may be included at certain stagesof the operation.

It is to be understood that modifications may be made in our processwithout departing from. the spirit of our invention and that we intendto be limited only by the appended claim.

What we claim as new and desire to secure by Letters Patent is:

A process of cyanide neutralizing pickled iron and steel sheets to besubsequently coated, in which the cyanide solution is maintained at atemperature from 140 F. to 180 F., at a concentration of from .120 to.150 ounce per gallon of solution, and in which the duration of the3;..-

from 4 to 40 seconds.

RUSSELL R. SMITH. HILLARD E. MILLER. RALPH H. GELDER.

neutralizing step is

